Since the code is mainly about Sheet Set via its COM API. So, it has very little to do with AutoCAD API itself. In terms of building error, you really should have include more details on what the errors are, or attach pictures to show the errors.

But, I would guess the errors would most likely come from the COM API reference "AcSmComponents2x.tlb", where 2x could be 21, 22, 23, depending on AutoCAD version. So, check the "References" in the VS project to make sure you have correct version Sheet Set COM API library references, corresponding to your AutoCAD version (for AutoCAD2018, it is 22), besides the correct version of AutoCAD .NET API references, of course.